Electronic telephone exchange



.Dec- 27, 1949 I' E. M. DELORAINE ETAL 2,492,136

ELECTRONIC TELEPHONE EXCHANGE 4 Sheets-Sheet 1 Filed March 14, 1946 9.25 Nr.5 ob,

. INVENTOR.

EDMQND M. DELORAINE BDxf/AVID H. RANSOM A TTORNE'V Dec. 27, 1949 E. M. DELORAINE ETAL ELECTRONIC TELEPHONE EXCHANGE Filed March 14, 1946 4 Sheets-Sheet 3 LINE SELECTING EQUIPMENT FIG. 3

Y INVENTOR.

EDMUND M DELORAINE g/VID H. RANSOM A TTOR'NEV Dec. 27, 1949 E. M. DELoRAlNE ETAL 2,492,136

ELECTRONIC TELEPHONE EXCHANGE F1144 March 14, 194e v 4 sheets-sheet 4 s 0 i 4: @L

E I 4 v MI E v RINGING CIRCUIT DIAL GATE

CONTROL AAM-I DIAL PULSE l RINGING CIRCUIT INVENTOR. EDMOND M. DELORAINE DAVID H. RANSOM Patented Dec. 27, -1949 UNITED STATES PATENT'OFFICE ELECTRONIC TELEPHONE EXCHANGE Edmond M. Deloraine, Paris, France, and David H. Ransom, Montclair, N. J., assgnors to Federal Telecommunication Laboratories, Inc., New York, N.v Y., a corporation of Delaware Application March 14, 1946, Serial No. 654,326

19 Claims. (Cl. 179-18) This invention relates to new and useful improvements in communication systemsand more ing signal from the central exchange to the called i line.

In accordance with the embodiment here disclosed two electronic means such as cathode ray tubes are provided in common for the lines. Signals such as dial and speech signals may be sent from both the calling and the called lines through one of the cathode ray tubes, and the signals such as speech and ringing signals may be sent to the line through the other cathode ray tube.

These and other features of the invention will more readily appear from the appended claims and the following detailed description of a preferred embodiment, of which as much as is necessary for an understanding of the invention is illustrated in Figs. 1 to 4 of the drawings. In reading the drawings, Fig. 2 should be placed below Fig. 1, Fig. 3 to the right of Fig. 2 and Fig. 4 to the right of Fig. 1, Figs. 1 and 4 being kept horizontal and Figs. 2 and 3 in vertical.

Fig. 1 shows the substation equipment of one line and the two electronic means and associated equipment common to the lines, the upper part of Fig. 2 the line finder, and the lower part the talking circuit and signal repeater equipment, Fig. 3 the registering and line selecting equipment and Fig. 4. the dial pulse and ringing equipment.

Each subscribers'line is provided with a subset I of any conventional type, a calling dial 2 by means of which, in the embodiment here disclosed, one to twenty impulses may be sent depending on the designation of the called line, a hybrid coil 3, and a balancing network Il. The interconnection of calling and called lines is eilected by means of a pair of cathode ray tubes of which 5 is employed for receiving signals (in-v cluding speech) from the line and 6 for transmitting signals (including speech, ringing, and the like) to the lines. The lines terminate on electrodes forming dynodes in the cathode ray tubes, one winding of the hybrid coil 3 being con- 6. Each tube is equipped with` the customary gun structure and deilecting means for the purci? pose of sweeping cyclically and in succession the line terminal electrodes provided therein. The beams of these tubes may, for instance, rotate (assuming that the line terminals are arranged in a circle) under the control of a master oscillator 'I operating at 200 kc. and connected in multiple with the deilecting plates of the two tubes through a 10 kc. frequency divider 8 and a 90 phaser 9, insuring a repetition rate of 10 kc. per second of the scanning beam.

When the subscriber at station I initiates a call the operation of the switch hook (not shown) at the subset I places a negative potential on the anode I2 through the dynode of the calling line in the receiving tube 5 over a circuit extending.

from the negative pole of grounded battery I0 over a retardation coil II, a loop including the secondary of the hybrid coil 3, the subset I, and dial 2. This causes a flow of electrons from the terminating electrode in the tube to anode I2 each time the scanning beam sweeps over the dynode of this line. The resulting negative pulse I3 is fed to the grid of a cathode follower and inverter tube I4. The negative pulses I5 in the cathode output of tube I4 are applied to the grid of a clipper amplier tube I6. Tube I6 is normally biased by resistor I'I to draw current, and the signal amplitude is so adjusted that each negative pulse I5 will drive the tube I6 beyond cut-off whereupon the tube will clip variations caused in the signal by dial pulses or transmitter modulation.

The positive pulse I8 appearing in the plate output of tube I6 is fed to the grid of cathode follower I9 and through the cathode thereof to conductor 2U which is multiplied to the grids of all line finder gate tubes 2l.

The line nder gate tubes 2 I are normally lbiased through battery 22 far enough beyond cutoff so that the incoming positive signal I8 will not affect their plate output.

A lock-in oscillator 23 in the line finder operates at a frequency slightly below the rate of scanning in the tubes lEl and 6 (200 kc), andvdi-` vides this output to a frequency of approximately kc. The sine wave output of oscillator 23 passes through a clipping amplifier and difierentiating circuit 24 in the form of pulses 25 to a multivibrator 26 arranged to synchronize at apl short square pulse 3| of approximately 5 microseconds duration. The trailing edge of the pulses 29 is suppressed in tube 30.

The negative pulse 3| is passed through a cathode follower 32 as pulse 33 which is applied to the cathode of the line finder gate 2l. rThe amplitude of pulse 33 is adjusted by delay gain tube 34 so that normally the line nder gate tube 2i remains cut 01T. This gate has a positive pulse I8 applied to its grid and a negative pulse 3S to its cathode, neither of which will drive it beyond cut-ofi to produce conduction. Since the lock-in oscillator 23 has a frequency which is slightly less than that of the master oscillator 1, the pulse 33 will drift with respect to the pulse i3 until the two will occur simultaneously whereupon the bias of the line finder gate tube is overcome. When this happens then a negative signal 34 appearing in the plate is passed through a rectifier 35 and an integrating net 36 to the grids of the delayed gain tube 34 and of the gate control tube 31. The latter will be driven to cut oi after a few pulses 34 have reached it, permitting the lockin gate tube 38 to pass a signal received from the master oscillator i over a wire 39. The output of the lock-in gate tube 38 will synchronize oscillator 23 with oscillator 1. A phase corrector fill inserted between the plate of grid 38 and the oscillator 23 insures accurate adjustment.

The portion of the rectified output of rectiner 35 which Was fed to the grid of the delayed gain tube 34 will drive the latter beyond cut-o after a few pulses. The plate of tube 34 and the screen grid of clipper gate 3!! are connected to a conimon resistor 4I. The screen voltage of gate 3d will, therefore, rise and will cause an increase in the amplitude of pulse 3| and, therefore, of pulse 33 which is the pedestal pulse applied to the cathode of line nder gate 2i. This will cause the grid of tube 2| to be driven positive by the pulse I8 and clipping by grid current will occur. However, the amplitude of the incoming pulse I8 will be insuicient to affect the line nder gate tube of any other link.

The output pulses 34' of the line iinder gate are supplied also over conductor 42 to the grid of an input gate control tube 43. The plate of tube 43 is connected in multiple to the suppressor grids of two tubes; one of these is an input gate ,i

tube 44 whose pair is 45, and the other is an output gate tube 46 whose pair is 41. The two pairs of input and output gate tubes 44 and 46 are ncrmally biased to cut-off on the suppressor grid by the voltage drop in plate resistor 48 of the input gate control tube 43. Similarly, the input and output gate tubes 45 and 41 are normally biased to cut-ofic on their suppressor grids by the voltage drop in plate resistor 49 of output gate control tube 50.

The negative pulse 34 coming from the line lnder gate drives the grid of control tube 43 beyond cut-off which will reduce the voltage drop across its plate resistor 49 to zero. This will raise the bias on the suppressor grids of gates 44 and 46, permitting the passage of signals which may appear on the control grids of these gate tubes,

It is assumed that speech and dial pulses will modulate the line signal at, say, The clipping action of tube I6 will cut-off the modulated `portion so that the pulse I8 which is applied to The pulses produced by the dial 2 of the calling line will thus be transmitted as pulses 54 under control of gate control 43, and through the plate of input gate 44 over conductor 56 and a pulse stretcher and integrating network 51 to the grid of an amplifier 58 in the form of positive pulses 59. These low frequency dial pulses 59 are amplified by tube 58 and shaped in a clipper tube 60 to form negative square wave pulses II. The pulses 6I are diierentiated in a network 62 into pulses 63 which are applied to the control grid of dial gate tube 64. The latter is biased so that the leading edge of the differentiated pulse S3 is suppressed and the trailing edge thereof is passed as a negative pulse 65 over conductor 65 to the register circuits.

The pulses 59 are passed in parallel over a pulse stretcher and integrating net H2, and the leading edge of the first pulse of a series flips conduction from tube B1 to tube 68 in the dial gate control. The circuit constants are such as tc maintain this condition until the end of the dial pulses when tube 61 again becomes conducting and sends a negative pulse to the dial gate control 69, 18 and to the ringing gate control 3&2, I03. The output of tube 1l) is applied over conductor 1I to the suppressor grid ofdia1 gate 6d, biasing the latter to -cut off. This will lock out the register so as toy protect it against transients.

The register circuits are also conventional Eccles-Jordan trigger circuits connected to form a strip count. Initially, the right-hand tube 13 of the No. 0 register and the left-hand tube 14 in the No. 1 register and of all subsequent registers are conducting. The rst negative pulses 65 on conductor 55 will transfer conduction in the No. 0 register from tube 13 to tube 12. The negative pulse appearing in the plate of tube 12 will be applied to the grid of tube 14 in the No. 1 register so as to transfer conduction to tube 15 of the latter. Y

The next pulse 65 will produce the same operations as above explained, except that now registers Nos. 1 and 2 will be involved. After a series of pulses 65, representing the dial pulses at the calling station, have been received, the righthand tube of one of the registers will be in conducting condition. A potential will be applied to the suppressor grid of the corresponding time channel gate tube 18, 19 or 88 associated with this register, permitting the passing of a signal from the control grid of the time channel gate.

The line selecting circuit proceeds now tc count the digit pulses as set in the register, synchronizing on each. count with a Zero pulse 8I applied to the No. 0 counter over a conductor 82 from a zero pulse generator 83 which is driven by the 10 kc. frequency divider 8.

Normally, the vleft-hand tubes 8d, 8E, 88, etc. 9B of the counters are conducting. The synchrom nizing pulse 3! flips conduction in the No. 0 counter from tube 84 to tube 85. Negative pulses 92 which are derived from master oscillator 1 over conductors 39 and 93 and a pulse-shaping amplifier 94 at 5 microsecond intervals are applied over a common conductor 95 to the grids of all the right-hand counter tubes 85, 81, 89 and SI.

The negative pulse 92 following the synchronizing pulse 8l will transfer conduction in the No. 0 lcounter from tube 85 to tube 84. The negative pulse appearing in the plate circuit of 84 is applied to the grid of the left-hand tube 86 in the N'o. '1 counter and will flip conduction to 81.

Each successive pulse 92 will flip a counter so as to make its right-hand tube conducting until the No. 1 register is conducting on its right-hand tube 15, then the positive bias on it is transferred over conductor 98 to the suppressor grid of time channel gate tube 18, so that when the No. 1 counter flips conduction to its right-hand tube 81 la negative signal 96 will be generated on the plate of tube 18.

The negative pulse 96 is applied overa conductor 99 and a busy pulse-shaping amplifier |00 to the grid of a busy gate tube IIV whose output added to the pulse I8 appearing in conductor 20 when the beam of sweeps the called line will prevent the operation of a line iinder gate tube like 2| when the called subscriber answers.

At the end of a series of dial pulses a negative pulse in the output of dial gate control tube 61 will ilip conduction from a tube |02 to a tube |03 in the ringing gate control forming part of the ringing circuit. This will permit a ringing gate tube |04 to send aringing signal over conductor |05 to the control grid of the output gate tube 41. Whenever the beam of the sending tube 6 sweeps over the dynode in which the called line terminates, ringing signal is applied through the following circuit: From a ringing oscillator |06 to the suppressor grid of ringing gate I 04 which has been made operative by the potential applied to its control grid by the ringing gate control, the plate of tube'I04, conductor |05, the control grid of output gate tube 41, the plate of tube 41, amplilier |01, the control grid of a pentode |08 whose suppressor grid is controlled over conductor |09 by the dial gate control 69, 10, the plate of tube |08, conductor IIO and the control grid III of the v sending tube 6. The grid I II will so control the beam when it impinges on the dynodes of the called line as to cause the operation of a ringer at the called station.

When the beam of tube 5 next engages the terminals of the called party who has answered, the positive signal I8 on the cathode of triode I9 will be applied over conductor I I3 to the control grid of trip ringing tube II4. This tube is now open p by virtue of a positive pulse applied toits suppressor grid by triode I I5 which, in turn, is made at this instant conductive by pulse 96 applied to it by the corresponding time channel gate over the beam of receiver tube 5 over the anode I 2, the f cathode follower I4 to the clipper tube 5I, and thence to the cathode follower 53 and over conductor 55 to the control grid of the input gate tube 44. From the plate of input gate tube 44, the

signal goes through a low pass lter II1 where it istransformed from a series of pulses to the original speech frequency signal and applied to thevcontrol grid of the output gate 41.5 From the plate ofthe output gate the signal passes through theamplifier |01, the tube |08 and conductor IIO to the control grid I I I of the sending distributor 6,

and through the appropriate dynode thereof to the called line.

The path of the speech signals from the called line to the calling line will be the same as above described but it will occur when the receiving distributor 5 sweeps over the dynode of the called line and the distributor 6 sweeps over the dynode of the calling line. Furthermore, the pulses 54 applied over conductor 55 will not affect the input gate 44 but the input gate 45 through whose plate it will be conveyed via another low pass lter |I8 to the control grid of the output gate tube 46, the output circuit of which is in multiple with the output circuit of the gate 41.

It will be seen, therefore, that the timing of the two functions is reversed, the input gate control tube 43 operating input gate 44 and output gate 48, and the output gate control tube 50 controlling the input gate tube 45 and the output gate tube 41.

At the termination of a call, when the calling subscriber hangs up, all circuits are released under the control of the delayed gain tube 34. The register circuit and the dial gates whichare locked in are released by the release tube II9, |20 and I2I. When the call is initiated the delay gain tube 34 is driven to cut oli, reducing the potential on the grid of tube |20 which is connected with the cathode of the delay gain tube 34 over conductor |22. This causes the obvious nip-flop circuit to transfer conduction to tube |I9 which sends a negative pulseV through a differentiating network to the grid of tube I2I. The latter is biased beyond cut-oil" and the pulse has no effect. When, however, the line nder 2| releases, then I I9 again becomes conductive and applies a positive pulse to the grid of I2 I. A negative pulse |28 will then be applied to the conductor |24 which will restore all the registers and the dial gate control tubes to normal.

What we claim is:

1. In a communication system, a plurality of lines, two electronic means common to said lines, each having a plurality of yelectrodes in which the lines terminate and means for cyclically signals originating on calling and called lines when the beam ofthe second of said electronic means sweeps over their terminals.

2. The system according to claim 1, and in which each electronic means comprises a cathode ray tube.

3. The system according to claim 1, in which the signal repeater comprises a discharge tube having input and outputA circuits, means for effectively associating the input circuit with the electrodes of the calling and called lines when they are swept by the beam in the second electronic means, and means for eiectively associating the output circuit with the control grid when the beam of the rst electronic means sweeps the electrodes ofthe calling and called lines. Y

4. The system according to claim 1, a plurality of signal repeaters, means operative upon the initiation of a call for taking into use one of said repeaters, and means for releasing the repeater taken into use upon the termination of the call. A

5. The system according t ing vmeans common to said lines, means foreach o claim 1', line selectline to control the selecting means to select the called line, and means for operatively associating said selecting means with the calling line.

6. The system according to claim 1, a plurality of ine selecting means common to said lines, me ns associated with the second electronic mens for controlling the selecting means to selec the called line, and means for operatively associating one of the selecting means with the second electronic means upon the initiation of a call.

7. The system according to claim 1, signalling means common to said lines, line selecting means common to said lines, means associated with the calling line to operate the selecting means to select the called line, and means operative thereupon for associating said signalling means with said repeater.

8. The system according to claim 1, and a hybrid coil for each line having a winding connected with an electrode of the second electronic means.

9. The system according to claim l, and a balancing network for each line.

10. In a communication system, a plurality of lines, electronic means common to said lines and having a plurality of electrodes in which the lines terminate and means for cyclically sweeping the electrodes with an electron beam, a control grid for the beam, a source of signals common to said lines, a signal repeater having an output connected with said control grid, timing means forapplying to the repeater signals originating on calling and called lines when the beam of said electronic means sweeps over their terminals, and means controlled by said timing means for applying signals from said source to the repeater when the beam sweeps over the terminal of the called line.

11. The system according to claim 10, and means for disabling the last-mentioned means controlled over the called line.

l2. The system according to claim 10, and in which said source comprises an oscillator, a connection for actuating said repeater by said oscillator, means controlled by the timing means for establishing said connection and means controlled by the called line for disestablishing said connection.

13. In a telephone system, a plurality of lines, two cathode ray tubes common to said lines, each having a plurality of electrodes in which the lines terminate and means for cyclically sweeping with an electron beam the electrodes, a control grid for the beam of the rst tube, a signal repeater comprising two input and two output gate tubes, each of said gate tubes having a cathode, an anode, a control and a suppressor grid,v means including the second cathode ray tube for applying signals originating on the calling and called lines tothe control grids of the input gates, connections including low pass lters from the anodes of the input gates to the control grids of the output gates, a connection for applying a potential to the suppressor grids of one input and one output gate controlled by the calling and called lines when their terminals are swept by the beam of the second cathode ray tube, a connection from the anodes of the output gates to the control grid of the first cathode ray tube, a connection for applying a potential to the suppressor grids of the other input and output gates when the beam of the second cathode ray tube sweeps over the terminals of the called line, a pentode in the connection leading to the control grid and having its anode connected to the latter and its control grid to the anodes of the output gates, and means controlled by signals over the calling and called lines for applying potentials to the suppressor grid of said pentode.

14. In a communication system, a plurality of lines, two electronic means each having means for moving a beam oi electrons and a plurality of electrodes in which said lines terminate, means for operating said electronic means continuously and cyclically to sweep said electrodes with their beams, a plurality oi signal input and'signal output tubes provided in pairs, means operative upon the initiation of a call on a line for selecting an input and output tube, input, output and control circuits for the selected tubes, means for operating the control circuits to render the selected pair of tubes eiective when the beams sweep the electrodes in which the calling and called lines terminate and ineiective at all other times, a connection from the output of the input tube to the input of the output tube, means for associating the input of the input tube with the electrodes in i one electronic means in which the calling and called lines terminate when they are swept by the beam, a control grid for the other electronic means, and means for connecting the output of thev output tube with said control grid when the electrodes of the calling and called lines are swept by the beam.

15. The system according to claim 14, and in which each electronic means comprises a cathode ray tube.

16. The system according to claim 14, and in which the input and output tubes have cathodes, anodes, control grids and suppressor grids.

17. The system according to claim 14, and in which the input and output tubes are pentodes.

18. The system according tov claim 14, in which the means for selecting the pair of tubes comprises a normally inactive line finder gate tube. means for actuating said line iinder gate tube upon the initiation of a call, and means for operating the last-mentioned tube to convey signals -from the electrodes of the calling and called lines in said one electronic means to the signal input tube whenever the electron beam sweeps over the terminating electrodes thereof.

19. In a telephone system, a plurality of lines, a sending and a receiving cathode ray tube commonto said lines, each tube having a plurality of electrodes in which the lines terminate, and means for cyclically and successively sweeping With an electron beam the electrodes, a control grid for the sending tube, a signal repeater having an output connected with said control grid and timing means for applying to the repeater speech signals originating on calling and called lines when the beam of the receiving tube sweeps over their terminals.

EDMOND M. DELORAINE. DAVID H. RANSOM.

REFERENCES CITED The following references are oi record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,185,693 Mertz Jan. 2, 1940 2,263,369 Skillman Nov. 18, 1941 2,265,216 Wolf Dec. 9, 1941 2,379,221 Espenscheid June 26, 1945 2,379,715 Hubbard July 3, 1945 2,387,018 Hartley Oct. 16, 1945 

